     (ContextStatementImpl. (->sesame-rdf-type (pr/subject this))
                            (->sesame-rdf-type (pr/predicate this))
                            (->sesame-rdf-type (pr/object this))
-                           (->sesame-rdf-type (pr/context this))))
+                           (when-let [context (pr/context this)]
+                             (->sesame-rdf-type (pr/context context)))))
 
   Value
   (->sesame-rdf-type [this]

       (->sesame-rdf-type [this]
         (LiteralImpl. str))))
  ([str lang-or-uri]
     {:pre [(string? str) (or (string? lang-or-uri) (keyword? lang-or-uri) (instance? URI lang-or-uri))]}
     (reify Object
       (toString [_] str)
       ISesameRDFConverter

  (.intValue literal))

(defmethod literal-datatype->type "http://www.w3.org/TR/xmlschema11-2/#string" [literal]
  (s (.stringValue literal) (.getLanguage literal)))

(defmethod literal-datatype->type "http://www.w3.org/2001/XMLSchema#dateTime" [literal]
  (-> literal .calendarValue .toGregorianCalendar .getTime))
